[gcc(refs/vendors/microsoft/heads/main)] Add a workflow to test current upstream gcc.

[Eugene Rozenfeld <erozen@gcc.gnu.org>]

https://gcc.gnu.org/g:a6ff5881b0236647f736b0ba5487c8c1b89e1b7f

commit a6ff5881b0236647f736b0ba5487c8c1b89e1b7f
Author: Eugene Rozenfeld <erozen@microsoft.com>
Date:   Fri Nov 13 14:53:21 2020 -0800

    Add a workflow to test current upstream gcc.

Diff:
---
 .github/workflows/fetch-rebase-test.yaml | 41 ++++++++++++++++++++++++++++++++
 1 file changed, 41 insertions(+)

diff --git a/.github/workflows/fetch-rebase-test.yaml b/.github/workflows/fetch-rebase-test.yaml
new file mode 100644
index 00000000000..85133ec749f
--- /dev/null
+++ b/.github/workflows/fetch-rebase-test.yaml
@@ -0,0 +1,41 @@
+name: fetch-rebase-test
+
+# Run this workflow every week
+on:
+  schedule:
+    - cron: "0 8 * * 0"
+  workflow_dispatch:
+
+jobs:    
+  fetch-rebase-test:
+    runs-on: ubuntu-18.04
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+        with:
+          fetch-depth: 0
+          submodules: recursive
+          lfs: true
+          ref: current
+      - name: Add remote
+        run: |
+          git remote add gcc git://gcc.gnu.org/git/gcc.git          
+      - name: Fetch
+        run: |
+          git fetch gcc master
+      - name: Rebase
+        run: |
+          git log gcc/master -1
+          git config --global user.email "erozen@microsoft.com"
+          git config --global user.name "Eugene Rozenfeld"
+          git rebase gcc/master
+      - name: Check commits
+        run: |
+          git status
+          git log -15
+                
+      - name: Run build script
+        run: | 
+          chmod +x .github/scripts/build-gcc.sh
+          .github/scripts/build-gcc.sh
+        shell: bash